Jonathan has been consistently listed as a leading tax Barrister by reference to recommendation for international corporate tax and particular expertise in transfer pricing in Chambers' Guide to the Legal Profession and the Legal 500. In the Chambers Guide he is commended for his ‘encyclopaedic knowledge of double tax treaties’ and described as “clearly amongst the best international tax barristers”. In Who's Who Legal UK Bar 2016, he is lauded for his “brilliant handling of cross-border tax problems”. In Chambers UK Bar 2018 he is “highly regarded for his expertise in international tax matters.” In the Legal 500 UK Bar 2019 he is rated as “the leading advisor on international tax treaty issues.” In Chambers UK Bar 2020 he is identified as "The double tax guru" with “extraordinary depth of knowledge and experience when it comes to tax treaty issues, and is a creative thinker and a clear and meticulous writer."

He is a visiting Professor at the Dickson Poon School of Law, King’s College London where he is Programme Director of the International Tax Law LLM.

Jonathan served on the EU Commission Group of experts on removing tax problems facing individuals who are active across borders within the EU from June 2014 to November 2015 and was appointed to the Permanent Scientific Committee of the International Fiscal Association in September 2016.

Major Publications: Schwarz on Tax Treaties (Wolters Kluwer): definitive, in-depth analysis of tax treaties under UK EU and international law. Booth and Schwarz: Residence, Domicile and UK Taxation (Bloomsbury Professional): the leading work on residence of individuals, companies, partnerships and trusts.